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Can Seawater Batteries Replace Lithium?

Irina Slav

Lithium and cobalt: the two components of a rechargeable battery that have spurred a research and development rush may eventually meet their match in the future, in a simple element available in abundance in seawater.

Sodium, unlike lithium is widely available everywhere there is saltwater. And since saltwater makes up the bulk of the Earth’s surface, it’s safe to say that it is quite abundant and easy to access. It also has properties that make it an excellent substitute for the lithium in batteries.

The challenge, however, is the electrodes. For this type of battery, better electrodes would be necessary.

A research team from the University of Southern Denmark is currently working on new electrodes that are made of iron, phosphorus, and manganese. According to the lead researcher, USD associate professor Dorthe Bomholdt Ravnsbæk, manganese is the key element. Thanks to it, the sodium ion battery that her team is developing has higher voltage and a greater energy storage capacity.

The Danish team is working in partnership with the University of Technology and the Massachusetts Institute of Technology to address two of the problems associated with the now dominant lithium ion technology.

One of these, of course, is the relative scarcity of lithium supply and, more than that, the fact that the world’s reserves of the metal are concentrated in just a handful of places. There used to be talk of a lithium shortage a couple of years ago that caused prices to shoot up, but the rally ended when it became clear that EV sales had not yet lived up to the hype. But now, lithium prices are on the rise again not least because of ambitious EU plans for cutting emissions by encouraging EV manufacturing.

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The other problem is cobalt. Here, the problem is more moral: the bulk of the world’s supply of cobalt is located in the Democratic Republic of Congo where human rights violations are rife. In addition to the ethical concerns, this concentration of cobalt makes it more expensive. The sodium ion battery that Bomholdt Ravnsbæk and her colleagues are working on does not use cobalt at all, so this will be one problem that is instantly solved.

Another fact that makes sodium-ion batteries a serious contender is that they can be produced at any factory that also produces lithium ion batteries. It won’t make much difference for troubled European carmakers that are now trying to tackle a battery shortage because they rely entirely on imported batteries, but it could make a transition from lithium ion to sodium ion batteries easier and cheaper.

There are, of course, drawbacks as there are with every technology. For now, it is difficult to fit the sodium ion battery into a small space, so it will be a while before sodium ion batteries replace the lithium ion batteries of smartphones. Yet they can be made into large batteries and used for energy storage: a growing field of interest for battery researchers.

Some sodium batteries are also prone to breaking because their cathode swells and shrinks during charging and recharging, and, more importantly, they have lower energy density than lithium ion equivalents because of the larger size of the sodium atoms.

Yet size does not always matter; more and more solar and wind energy tenders require the bidders to include energy storage in their offers. A cheaper but comparably efficient battery than lithium ion ones could be instrumental in bringing down the costs of solar and wind installations with storage.

Bomholdt Ravnsbæk and her team are currently working on shortening the charging times of their sodium ion battery and extending its life.

By Irina Slav for Oilprice.com

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